B737NG飞机反推系统故障分析

根据波音的相关技术文件,B737NG反推系统的部件有些本身带有设计缺陷或可靠性较低,导致反推系统故障较多。对反推系统的工作原理、常见故障及处理方法进行总结,使排故人员和故障管控工程师对该系统有深入的了解,方便大家开阔思路,减少排故的时间,提高排故效率。     

高强度铝合金小裂纹疲劳扩展规律研究

考虑了高强度铝合金表面局部塑性变形特点，并引入小裂纹尖端屈服应力的渐变规律，分析了裂纹尖端屈服应力的这种变动对裂纹张开应力变动规律的影响，同时它还与Ｔ应力共同作用使得线弹性断裂力学不再适用于预测小裂纹尖端塑性区。据此可以解释小裂纹扩展的规律，并与高强度铝合金的实验结果基本吻合。     

Algorithm and experiments of six-dimensional force/torque dynamic measurements based on a Stewart platform

Stewart platform (SP) is a promising choice for large component alignment, and interac-tive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation (P&O) adjusting platform, based on an SP for force/torque-driven (F/T-driven) alignment, can dynamically measure interactive forces. This paper presents an analytical algorithm of measuring six-dimensional F/T based on the screw theory for accurate determination of external forces during alignment. Dynamic gravity deviations were taken into con-sideration and a compensation model was developed. The P&O number was optimized as well. Given the specific appearance of repeated six-dimensional F/T measurements, an approximate cone shape was used for spatial precision analysis. The magnitudes and directions of measured F/Ts can be evaluated by a set of standards, in terms of accuracy and repeatability. Experiments were also performed using a known applied load, and the proposed analytical algorithm was able to accu-rately predict the F/T. A comparison between precision analysis experiments with or without assem-bly fixtures was performed. Experimental results show that the measurement accuracy varies under different P&O sets and higher loads lead to poorer accuracy of dynamic gravity compensation. In addition, the preferable operation range has been discussed for high-precision assemblies with smal-ler deviations.     

Scheme design of the CHANG’E-5T1 extended mission

Flight schemes for the CHANG’E-5T1 extended mission are investigated in this paper. In the flight scheme and trajectory design, the remaining propellant of the CHANG’E-5T1 mission is utilized. The CHANG’E-5T1 mission is firstly introduced with feasible flight goals derived based on the terminal trajectory and satellite status. The flight schemes are designed to include a lunar return and the libration points in the Sun-Earth/Moon and Earth-Moon systems, with an emphasis on the Earth-Moon triangle libration point thus far unexplored. Secondly, three schemes are proposed for the CHANG’E-5T1 extended mission with different flight goals. The direct libration point orbit transfer and injection method is adopted to solve the issue in the transfer trajectory design. Furthermore, an innovative concept is proposed to transfer from the Earth-Moon collinear libration point to the triangle point using the Sun-Earth/Moon libration point. Finally, the merits and drawbacks of the three schemes are discussed in terms of flight time, control energy and frequency, flight distance, and goal value. As a result, the scheme including a lunar return and the Earth-Moon L2 libration point is selected for the CHANG’E-5T1 extended mission. A flight to the Earth-Moon libration point is achieved, replicating the achievement of the ARTEMIS mission.     

任意K元Huffman树的新构造

给出了一种简单而有效地构造任意k元最优Huffman树的新方法。给出了Huffman村存贮的父母一子女环结构,该结构空间利用率高,在不增加parent域的情况下,使查找父母的T（m）达到O（1）,并能高效实现建立最优Huffman树和求Huffman编码的算法,无论是空间复杂度还是时间复杂度均优于传统算法,具有很强的实用性。     

2024T4铝合金蠕变本构关系研究

设计了一种简易单向拉伸蠕变试验装置,对2024T4铝合金在175℃、多个应力水平下的单向拉伸蠕变进行了试验。根据试验数据的特点,将2024T4铝合金的蠕变本构关系分解为由一个双指数函数和一个一次函数组成的两分量表达式,并利用试验数据通过最小二乘拟合确定出本构关系中的待定参数,得到2024T4铝合金175℃时的本构关系。通过对拟合数据与试验数据的对比分析表明,所建立的蠕变本构关系能够有效表征2024T4铝合金175℃时在不同应力水平下的蠕变行为。     

FC网络通信中PCIe的接口的设计与实现

PCIe总线具有点对点串行连接、双通道、高带宽、链路数可选、在软件层与PCI保持兼容等特点,在嵌入式领域得到越来越广泛的应用。以XC5VFX130T芯片为硬件核心,分析PCIe的协议原理和XC5VFX130T芯片内嵌的PCIE Endpoint block硬核模块结构,实现具有PCIe系统主机接口的FC总线接口板卡,实现的功能和性能经过仿真和FPGA实现,达到了设计要求。     

机载电子电气设备缓蚀剂的评价

采用塔菲尔(Tafel)曲线法和电化学阻抗法(EIS)2种电化学方法评价了 4种不同型号的电子电气缓蚀剂在天然海水中对 T2铜合金、H62铜合金以及 2Al2-T4铝合金的缓蚀效果。对于 T2铜合金,缓蚀剂的缓蚀效率从高至低依次为 DZ-1、TFHS-20、DJB-823、WD-40;对于 H62铜合金,缓蚀效率从高至低依次为 DZ-1、DJB-823、WD-40、 TFHS-20;对于 2Al2-T4铝合金,缓蚀效率从高至低依次为 DZ-1、WD-40、DJB-823、TFHS-20。4种缓蚀剂中,DZ-1缓蚀剂 Tafel曲线法和 EIS法得到的缓蚀效率都高于 99.5%,所以,对于 T2铜合金、H62铜合金以及 2Al2-T4铝合金 3种金属材料来说,DZ-1是 4个型号的缓蚀剂中效果最优的。     

深空干涉测量天线G/T值指标设计

G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法.首先根据射电源的空间分布以及流量密度特性,确定了测地VLBI和航天器VLBI观测模式下射电源流量密度的要求.在此基础上建立了2种观测模式下时延误差与深空干涉测量天线G/T之间的关系模型.最后参考目前国际国内测地VLBI观测中的通用参数设置以及月球探测任务中航天器VLBI观测的参数设置,对不同观测任务、不同观测模式下的G/T要求进行仿真分析.综合测地VLBI和航天器VLBI观测仿真分析的结果,S频段G/T建议不小于32 dB/K,X频段G/T建议不小于43 dB/K.仿真分析结果可以作为后续深空干涉测量天线G/T设计的参考.     

工艺参数对2A97T3铝锂合金光纤激光焊接焊缝成形的影响

通过系统的工艺试验研究了1.2mm的2A97T3铝锂合金光纤激光焊接工艺参数对焊缝成形的影响。结果表明:增大焊接热输入会使焊缝熔宽及背宽比增加,其中背面熔宽变化显著,而正面熔宽变化幅度较小;焊接热输入过大时,会出现因焊缝下塌而导致熔宽减小的现象。随着焊接速度和激光功率的增大,形成深熔焊缝的参数范围会越来越窄。在线能量相同的情况下,高速焊所获得的焊缝成形较好,热导焊焊缝硬度明显高于深熔焊焊缝的硬度。